Field of the Invention
The present invention relates to an image capturing apparatus.
Description of the Related Art
In recent years, an image sensor with a structure capable of performing pupil-division type focus detection has been employed in digital cameras and digital video cameras. For example, in Japanese Patent Laid-Open No. 2001-124984, two photodiodes are provided in one pixel of an image sensor, and the two photodiodes are each configured so as to use one microlens to receive light that has passed through a different pupil area of the image capturing lens. Accordingly, phase difference detection type focus detection can be formed by comparing the output signals from the two photodiodes. Also, a captured image signal can be obtained by adding the output signals from the two photodiodes.
In Japanese Patent Laid-Open No. 2013-178564, a technique is described in which in the case where phase difference detection is performed with the image capture surface, the signals from G pixels are read out after performing horizontal adding, and the signals from the R and B pixels are read out without performing horizontal adding.
In a system of reading out output signals from two photodiodes such as those described above, there are cases where the subject is dark, there is a lot of noise, and the correlation operation for focus detection cannot be performed correctly.